Selector circuit



Sept. 13, 1966 H. F. MEYER 3,273,023

SELECTOR CIRCUIT Original Filed Feb. 20, 1961 2 Sheets-Sheet 1 I7 O |6:32?- 2 l5 0 f [4 O O E 0 O o O l? g O O O 5 0%: O O W= TOOL T1 T2 T3 T4T5 T6 T7 T8 T9 ABSCISSA 2| 22 23 24 25 26 27 28 29 3O 3 INVENTOR.

HENRY F. MEYER BY A NEYS Sept. 13, 1966 Original Filed Feb. 20, 1961H.F.MEYER SELECTOR CIRCUIT 2 Sheets-Sheet 2 INVENTOR BY HENRY F MEYER%av ;iy 77 A TORNEYS United States Patent 3,273,023 SELECTOR CHQCUITHenry F. Meyer, Cortland, N.Y., assignor to The Monarch Machine ToolCompany, a corporation of ()hio Continuation of application Ser. No.W505, Feb. 20, 1961. This application Sept. 25, 15 64, Ser. No. 399,23311 Claims. (#Cl. 317134) This application is a continuation of myapplication, Ser. No. 90,505, now abandoned, filed Feb. 20, 1961.

This invention relates in general to control circuits and, moreparticularly, to control circuits for use with tool pools or toolstorage means for a plurality of tools which may be used with a machinetool. The control circuit is useable to control the selected operationof a controllable device which, for purposes of illustration, may be amachine tool.

Heretofore devices have been provided in machine tool operating machinesfor directing the positioning of objects to be worked upon by one ormore tools in a preplanned or scheduled operation. Such a device maycomprise a manually operated directing device, or a coded or memorydevice which may be operated in conjunction with correlative electricalcontrol circuits for energizing suitable motors which actuate thepositioning equipment. These devices serve to eliminate personal errorswhich result from mis-locating the part to be tooled, but they do notprovide positive assurance that the particular tool will be used whichis scheduled for the instant operation. For example, in a boring machineoperation where for a scheduled bore a series of different tools are tobe used to turn out the finished job, such as a boring tool, a reamerand a threading tap, there is need for assurance that all these toolswill be used in the order named. A careless or unreliable attendantmight omit the use of the reamer and still produce a threaded bore, butwithout the reaming operation the ostensibly finished job would bedefective and subject to rejection.

Accordingly, it is among the objects of the present invention to providea control circuit which will secure the selection of actuation of aproper switch and this switch may be actuated by insertion or removal ofa tool from -a tool storage means.

Another object of the invention is to provide a control circuit whereinone selector switch must be actuated and all the other selector switchesof a given plurality must be unactuated before a given control circuitfunction will be accomplished.

Another object of the invention is to provide a control circuit whereina shunt circuit is established around an actuated open contact means ofa selector switch in order to provide an energization circuit for acontrollable device.

Another object of the invention is to provide a control circuit with aplurality of series connected contact means of a plurality of selectorswitches with these contact means normally being closed in the circuitas utilized, and with one of these contact means selectively being openand establishing a shunt circuit therearound to provide energization fora controllable device.

Another object of the invention is to provide means for controlling theuse of a scheduled tool, or a series of scheduled tools in a pre-plannedoperation of a tool operating machine.

Another object is to provide means for preventing a tool operatingmachine from being started until, or unless a pre-planned tool for agiven operation is selected therefor.

A further object is to provide a tool rack, storage means or pool fortools which are to be used in a scheduled operation, wherein a sole andindividual receptacle is provided for each tool, wherein a signal isprovided to indicate the tool to be used, and wherein the machine tool'ice may not be energized to carry out the intended operation unless, oruntil all the tools of the pool are in their proper places, except theone to be used in the instant operation, and the latter tool has beenremoved from the rack.

These and other objects of the invention will be more fully understoodfrom the following description which will be made with reference to theaccompanying drawings in which like numerals designate like parts, andin which FIGURE 1 is a partial side elevational view of a tool rack orpool which provides accommodation for as many as nine tools;

FIGURE 2 is a partial top plan view of the rack illustrating theindividual receptacles for the tools;

FIGURE 3 is a top plan view of a section of a memory device in the formof a tape which is perforated in accordance with a scheme hereinrepresented, and which may be utilized in the manner hereinafter to bedescribed for initiating the operation of the device;

FIGURE 4 is a schematic representation of a lamp connection in bank B ofthe stepping switch, showing the arrangement of a stepping switchcontact, a time delay switch and the lamp which is lighted when the toolto be used is selected; and,

FIGURE 5 is a schematic representation of one embodiment of theinvention which comprises an arrangement of electrical connectionsexisting when tool No. 6, as designated herein, is selected for use andis removed from the rack.

The objects of the invention are attained in general by providing thecombination of a tool pool, depot or rack having suitable electricalconnections and switches for closing one part of a selected circuit whenthe tool to be used in a pre-planned operation is removed from the toolrack; an adjustable four bank multiple contact stepping switch or gangswitch means in which one bank is a contact selecting first bank toselect a circuit corresponding to a given tool, said circuits beingprovided with solenoid or relay operated switches for opening andclosing the same; a coded memory device correlated to the lattercircuits which is arranged to control the energization of said relaysindividually; a suitably connected motor for cont-rolling the operationof the stepping switch and for moving it into different positionscorresponding to the several tools to be used in response to the memorydevice; means in a second bank of the stepping switch for indicating thetool to be used in the coded operation; a third bank of the steppingswitch controlling electrical connections to a power operated masterswitch and a master supplemental switch; and a series of contacts in afourth bank of the stepping switch for closing selected shunt circuits.

In operation, the invention comprises advancing the memory device, suchas the coded perforated tape 46 shown in FIGURE 3, into a scanningstation where a scanning device, or reader 47 operates to open aprearranged relay 41-44 circuit, or combination of relay circuits whichcorrespond to the tool to be used in the instant operation. Where acoded perforated tape 46 is used as the memory device, the horizontalrows of perforations correspond to the relay circuits and the verticalcolumns correspond to the different tools T1 through T9, respectively.One more horizontal and vertical position may be provided on the tapefor a zero position which represents the starting or homing position(FIGURE 5) of the stepping switch at the beginning of an operation. Forexample, FIGURE 3 shows how the tape may be coded for selecting the ninetools in numerical order. The first through seventh ordinates aredesignated by reference numerals 11 through 17, respectively. The firstthrough tenth abscissas are designated by reference numerals 21 through30, respectively. The circuit for the first tool Tl may be coded in thefirst abscissa position 21 by perforating the tape once in the firstordinate position 11. The second tool T2 is shown coded in the secondabscissa position 22 by a perforation in the second ordinate position12. The third tool T3 is shown coded in the third abscissa position 23by perforations in the tape in both the first and second ordinatepositions 11 and 12. The fourth tool T4 is coded by a perforation in thethird ordinate position 13, and so on according to a binary code. Thesixth tool T6 is shown coded in the sixth abscissa position 26 byperforations in both the second and third ordinate positons 12 and 13.The starting code on the tape for homing the stepping switch after atooling operation is completed may be a single perforation in theseventh ordinate position 17 and this is shown in the tenth abscissaposition 30. This homing position will select the starting position ofthe stepping switch 18 when the relay 45 (FIGURE is caused to bedeenergized and the contacts 45E of the relay are opened.

The stepping switch 18 may be considered gang switch means and has fourbanks, A, B, C and D. These four banks may be considered a contactposition selecting bank A, a tool indicator bank B, a master switch bankC and a shunt circuit bank D.

The stepping switch 18 has a motor or solenoid coil 48 actuating anarmature 98. The stepping switch also includes a scanning wheel 94 whichis engaged by a scanning wheel detent 95 to assure only unidirectionalrotation of the scanning wheel 94, in the clockwise direction shown bythe arrow. The armature 98 carries a pawl lever 97, in turn carrying apawl 96 for engaging the scanning Wheel to provide the unidirectionalrotation by one step each time the armature 98 is actuated.

The solenoid coil 48 is connected in a circuit which includes the firstand second leads 51 and 52 which may be the supply conductor and thereturn conductor from a suitable power supply source, not shown. Thismay be a direct current source or it may be an alternating currentsource if alternating current relays are used.

The stepping switch armature 98 is pivoted at 102 and a spring 99 urgesthe armature 98 away from the solenoid coil 48. An armature extension104 actuates an insulated button 100 of a normally closed interrupterswitch formed by a spring blade 105 and a contact 106, with theinsulated button carried on the spring blade 105. Each gang of thestepping switch has a wiper arm 19A-19D, respectively, carried on theshaft 93 of the stepping switch 18. Each wiper arm 19A-19D is insulatedfrom the shaft 93 and is electrically in engagement with a brush20A-20D, respectively. The solenoid coil 48 is connected to the firstlead 51 by a conductor 53 and is connected through a lead 54 to theinterrupter switch 105-106. The contact 106 is connected by lead 55 tothe brush 20A. Each wiper arm 19A19D in the respective banks of thestepping switch is adapted to electrically engage ten different contactsnumbered 1 through 10. These have the suffix A, B, C and D in therespective banks A, B, C and D. If the wiper arm 19A is at the contactpoint A and the relay contact 45E is open, then this will de-energizethe motor or solenoid coil 48 of the stepping switch 18. Theenergization circuit for this solenoid coil 48 is from leads 51 to 52by'way of conductor 53, lead 54, interrupter switch 105-106, lead 55,brush 20A, wiper arm 19A, contact 10A and conductor 56 through relaycontact 45E.

Accordingly, if there is a perforation in the tape in the seventhordinate position 17, as shown in FIGURE 3, this will cause steppingswitch 18 to return to the homing or starting position.

The wiper arms 19A-19D may be considered to be movable devices in thegang switch banks A, B, C and D to sequentially engage the contacts inthe respective banks. There are a given plural number of toolsselectable by the present circuit, and each gang switch bank hascontacts equal in number to said given plural number. In this case ninetools are selectable and nine contacts are used in each switch bank.Additionally, a tenth switch contact 10A is used in the first switchbank A for returning the stepping switch to the starting position. Atthe start of a stepping switch indexing operation the switch contact 45Eis closed, either manually or by means hereinafter described.

In practice the scanning device 45 needs as many scanning units as thereare ordinate positions coded on the tape. Seven ordinate positions areshown in the illustration of FIGURE 3. However, in this example of onlynine tools, only five scanning devices are needed and these are shown inFIGURE 5, the same being those corresponding to the relays 41-45. Theserelays control contacts according to a binary code in bank A of thestepping switch.

FIGURE 5 illustrates the disposition of parts and condition of thecircuit when the use of the sixth tool T6 is selected by the tape 46.Thus, in the first bank A, relay contacts 42C and 43C are open and thecorresponding relays 42 and 43 are de-energized. These relay contacts42C and 43C open all connections between the sixth contact 6A and thelead 52. The other relays 41 and 44 are energized, and the relaycontacts thereof are closed.

In the operation illustrated in the drawings, the sixth tool T6 isselected for use and is absent from the tool rack 109 (FIGURE 1). Aswill be more fully explained hereinafter the dwell or selection positionfor any tool such as tool T6 is the completely open orabsence-ofconnection in the group of conductors through the contacts ofrelays 4144 in level A (FIGURE 5). As shown, the contact 6A in bank A isconnected to relay contacts 42C and 43C which are open at this time, andthis deenergizes the stepping switch solenoid coil 48 to stop thestepping movement at the selected position, in this case for tool T6.All wiper arms 19A-19D stop in engagement with the respective sixthcontact 6A-6D.

It will be seen by reference to the perforated tape 46 (FIGURE 3) thatin order to control the illustrated system, there must be a total ofnine different combinations in the control bank A in order to form asufiicient number of combinations of circuits which are different. Thesenine combinations are correlated by the sixteen perforations shown inFIGURE 3, each of which is in a different position on the tape. Thus,there are five contacts 41A41E on relay 41 distributed relatively likethe five perforations in the first horizontal row or ordinate 11 of thetape 46. There are four contacts 42A42D on relay 42 spaced in the secondhorizontal row or ordinate 12 of the tape located so that differentcombinations of perforations will be opposite the several tool positionsrepresented by the abscissas in the tape of FIGURE 3. There are fourcontacts 43A-43D on relay 43 and two contacts 44A and 44B on relay 44.Also, there is relay contact 45E corresponding to the seventh ordinateposition 17. The latter is a special position to provide for a startingposition of the stepping switch at the beginning of an operation. Thedifferent combinations of connections in the switch bank A whichcorrespond to the related perforations coded on the tape provide abinary code to decimal code conversion to make the stepping switch stopat the correct one of nine selectable positions. Accordingly, when thestepping switch 18 is rotated by the indexing motor 48 in a clockwisedirection, as indicated by the arrow in FIGURE 5, the dwell or toolselection will take place on the contact point 6A where relay contacts42C and 43C are open.

When the open circuit position for tool T6 has thus been found, thewiper 19B in indicator switch bank B is turned to the correspondingcontact point 6B, as shown in FIGURE 5 and will close a connection whichenergizes an indicator, such as a lamp 6L of lamps 1L-9L, which may bedesirably located opposite tool T6 in the rack 109 to indicate that toolT6 is the one to be removed from the tool rack and used in the instantop eration. As will appear hereinafter, the machine tool 53 Cannot bestarted unless, or until tool T6 is removed from the rack and all othertools are in their proper places, when the use of tool T6 is selected bythe tape 46.

The tool rack 109, as illustrated in FIGURE 1, has positions for thenine tools T1-T9 and each tool actuates a switch. This may be a singlepole, double throw switch or it may be'two separate switches. Theswitches include first contact means 3139 and second contact means31'39', respectively, for the tools Tl-T9. As shown, the first contactmeans are normally open contacts and the second contact means arenormally closed contacts. As used in this circuit however, the normallyopen first contacts 31-39 are closed by insertion of the proper toolT1T9 in the tool rack 109 and at the same time, this opens thecorresponding second contact means 31'39.

In switch bank C the wiper arm 19C is caused to rest on a sixth contactpoint 6C which closes a connection from lead 51 through the tool-closedfirst contact means 39, 38, 37, switch 36 which is closed when tool T6is removed from the rack, lead 57, contact 6C, wiper arm 19C, lead 58,the coil of master switch relay 59 to lead 52. The energization of relay59 causes the normally open relay contacts 59A and 59B to close. Relaycontact 59A may be considered a master starter switch and relay contact59B may be considered a masfor supplemental switch. Provided tool T6 isremoved from the rack, switch 36' is closed by said removal and providedtools T7 to T9 are in place in the rack, then a closed circuit betweenleads 51 and 52 is formed from the lead 51 through the normally closedswitches 39, 38 and 37, closed switch 36 which is closed by the removalof tool T6 and lead 57 to the switch contact 6C. If however tool T6 isnot removed from the tool rack, the switch 36 will not be closed and therelay 59 consequently cannot be energized. The switch contacts 59A and59B will remain open so that a controllab'le device 68 will remaininoperative and unenergizable. The latter effect will likewise result ifall the tools from T1 to T or all the tools from T7 to T9 are notproperly seated in their respective places so that switch contacts 31 to35 or switch contacts 37 to 39 in the illustration will not be closed,as will presently appear.

Similarly, wiper arm 19D in the shunt circuit switch bank D will rest ona corresponding sixth contact point 6D and close a bridging connectionwhich bridges the switch connection that is broken by the opening ofswitch 36 when tool T6 is removed from this rack 109. This bridgingcircuit comprises lead 57, contact 60, wiper arm 19C, lead 58, relaycontact 59B, lead 61, wiper arm 19D, contact 6D and lead 62. When toolT6 is removed from the rack and all other tools are seated in theirproper positions, a closed circuit will then be established from thelead 51 through the switch first contact means 39, 38, 37, switch 36",lead 57, contact 60, wiper arm 19C, lead 58, recently closed switchcontact 59B, lead 61, wiper arm 19D, contact 6D, lead 62, the seriesconnection through switches 35 to 31 and to the closed master switchcontact 59A, all of which provides a live circuit to the controllabledevice 60. This controllable device 60 may include a starter buttonhaving starter button contacts 49 and a relay 64 having normally openrelay contacts 64A. The contact 64A may be connected in leads 84 and 85.This circuit may be closed thereafter by manually operating the starterbutton 50 to energize the power switch relay 64. When the operatormanipulates the starter button 50, the live circuit will be closedthrough the switch contacts 49 and relay 64 whereby power switchcontacts 64A will close the power supply lead 84 to lead 85 'forstarting the operation of the machine tool, as an example of acontrollable device. The power circuit 84-85 may be used in variousways, such as that of empowering the machine tool driving motor, toclose a clutch operating solenoid for cffecting the operation, orenergization of any other device whereby the machine tool will be causedto operate. Switch bank D and its connections are provided so as to beassured that tools T1 to T5 are all in their proper receptacles, eventhough tool T6 is removed from its receptacle and all other tools are inorder. In case all tools T1 to T5 are not in order the necessary seriescircuit through switches 35 to 31 and switch contacts 59A will bebroken, and an attempted energization of the relay 64 will beineffectual.

In the lamp circuit-s of switch bank B the insertion of time delayswitches is optional. Without time delay switches in the lamp circuitsthe lamps will flash as corresponding contacts are made with the severalcontact points, but when a suitably timed delay switch is inserted ineach lamp circuit, only the tool indicating lamp, or other indicator forthe tool to be used will become active. The connection in which a timedelay switch is utilized in the lamp circuit is illustrated in FIGURE 4.When the stepping switch is made to dwell on a given contact point, suchas contact point 6B in bank B, a circuit will be established from leadthrough wiper arm 19B, contact 6B, time delay relay 65 to lead 52.Resultantly the normally open indicator relay contacts 65A will beclosed after a short time delay, and lamp 6L or other tool indicatorwill be energized through the resulting closed circuit to the lead 52.

The switch contacts 45E in the lead 56 may be arranged to be closedmanually after the stepping switch has been indexed to the startingposition shown in FIG- URE 5, or it may be closed automatically byincluding in the memory system a special tape perforation and a scanningdevice operable to close the circuits of relay 45 across the leads 51and 52. In any event, the connection from contact 45E to lead 52 must beclosed in order that the stepping switch solenoid coil 48 may berendered operative at the start of an indexing cycle; and the sameconnection must have been opened in order that the stepping switch motor48 may be rendered inoperative after the finish of a tool operation,when the stepping is caused to be indexed to the starting position.

The tool rack 109 (FIGURE 1) comprises an elongated top plate 120 andenclosure within which the tool selector switches with contacts 31 to 39and 31 to 39' are mounted. The stepping switch 18 may be mounted in anyconvenient place, such as at housing at the left end of the enclosurenear the selector switch 39, and the power supply leads 51 and 52 may bebrought out through the casing, or otherwise conveniently arranged. Thetool receptacles 71 to 79 are secured to the top plate of the elongatedenclosure and receive a chuck to hold the individual tools. Key-ways areformed in the lower cylindrical extensions thereof, such as thevariously notched openings or slots 81-83 for the correspondingreceptacles 71-73 illustrated in FIGURE 2. The stems or shanks of thetool holders, such as stem 91 are machined to fit the diiferently formedopenings or slots in a manner such as that in which keys are made to fitcomplementary key ways in looks, so that in order that tool T1, forexample, may manipulate its corresponding microswitch 31, 31', it mustbe inserted in receptacle 71 which is the only receptacle with a keyway81 formed to permit this tool to be inserted to close switch contact 31and open its companion switch contact 31'. When a tool is removed fromthe rack 109, for example tool T6 from receptacle 76, the microswitchcontact 36 is opened and microswitch contact 36 is closed as illustratedin FIGURES 1 and 5.

A suitable scanning device 47 is illustrated in FIGURE 5 and comprisesas many scanning wheels as there are horizontal rows of perforations inthe tape or memory device, in the present illustration there are sevenrows; but for this illustration of only nine tools only four wheels areneeded for the tool selection plus a fifth scanning wheel for the homingposition. In FIGURE 5, scanning wheels 121, 122, 123, 124 and 127 areshown and are aligned to cooperate with the perforations in the first,second, third, fourth and seventh rows of the memory device 46. As thetape is advanced in the direction of the arrow shown in FIGURE 3, thetape perforations move into the reading position underneath the scanningwheels. The scanning wheels have elongated radially and outwardlyextending fingers which are sufiiciently slim to drop through theperforations in the tape, and do so when a finger and a perforation inthe tape coincide. For example, when the memory tape is displacedlongitudinally so that a perforation is aligned with a finger of wheel123, the finger drops into the perforation, thereby lowering thewheel-end of the respective lever 128 upon which the wheel 123 ismounted to rotate and wheel along the surface of the tape. Each lever128 has an insulated projection 129 above the wheel which bears upwardlyon the respective spring contact member 130 for permitting the contactmember 130 to move downwardly out of engagement with the respectivecontact point 131 when the wheel 123, lever 128 and spring contact 130are depressed.

Thus when the scanning wheel reads the intelligence stored on the tapeby dropping into the aligned perforation, the normally closed andnormally energized relay circuit corresponding to a certain horizontalrow of intelligence records, such as the third row 13 of the tape, isde-energized. In the example chosen of selection of tool T6, scanningwheels 122 and 123 have dropped into tape perforations, to de-energizeboth relays 42 and 43. This opens all relay contacts thereof. In thefirst, second and seventh rows of the tapethere are no perforations inthe reading position illustrated in FIGURE 5. Consequently, scanningwheels 121, 124 and 127 remain upon the surface of the tape, thecorresponding relay circuits remain in their normally closed conditionand relays 41, 44 and 47 remain energized.

When a particular tool operation is completed and a new tool is to beselected, upon tape advance toward the next intelligence point, movementof the tape will lift the scanning wheels 122 and 123 to energize relays42 and 43. This starts movement of the stepping switch 18 byenergization of the solenoid coil 48. When a perforation in the tape inthe seventh row 17 of the tape is encountered by the scanning wheel 127,this will operate in the manner just described to de-energize relay 45and open contact 45E to stop the stepping switch 18 in the startingposition. The relay 45 has normally closed contacts 45A-45D, connectedin parallel with the contacts 130-131 of the respective scanning wheels121-124. When relay 45 is de-energized, these contacts 45A-45D close tomake certain the relays 41-44 are all energized, so that the steppingswitch 18 will not stop until it reaches the homing or startingposition. In this condition the stepping switch is in position toreceive the next reading sent out by the memory device, at which timeand in which position of the tape the scanning wheel 127 will again bewheeling along the surface of the tape and relay 45 will be energized,and some one or more of the other scanning wheels will encounter codedperforations.

If desired other intelligence may be stored on the memory device, suchas directions for automatically operating the machine tool. Other kindsof memory devices can be used instead of the punched tape described,such as a punch card or a magnetic tape, provided a device capable ofreading the stored intelligence is also used and connected into thesystem described. Other codes than the numerical positioning systemhereinabove described may also be used.

From the foregoing disclosure it will be recognized that the inventionis susceptible of still other modifications without departing from thescope and spirit thereof, and

it is to be understood that the invention is not restricted to thespecific illustrations herein set forth, except insofar as they arespecifically limited by the terms of the appended claims.

What is claimed is:

1. A control circuit comprising, in combination, a con- .trollabledevice,

a master starter switch,

a plural number of selector switches each having first and secondcontact means with one thereof being open and the other thereof beingclosed,

a master switch bank having contacts arranged to correspond to each ofsaid selector switches,

a movable device in said switch bank engageable with the contactstherein to select a predetermined contact position for selecting adesired one of said selector switches,

a power operator for said master starter switch,

means for energizing said master starter switch power operator throughthe corresponding one of said second contact means and the predeterminedcontact position of said master switch bank upon the desired selectorswitch being actuated to open said first contact means and close saidsecond contact means thereof,

means including said master switch bank to establish a shunt circuitaround the actuated open first contact means of the actuated selectorswitch upon the desired selector switch being actuated,

and means for energizing said controllable device through the remainingones of said first contact means and through said shunt circuit upon thedesired selector switch being actuated.

2. A control circuit comprising, in combination, a controllable device,

a master starter switch and a master supplemental switch,

a plural number of selector switches each having first and secondcontact means with one thereof being open and the other thereof beingclosed,

gang switch means having a master switch bank and a shunt circuit bank,

contacts in each switch bank arranged to correspond to each of saidselector switches,

a movable device in each of said banks for sequentially engaging thecontacts therein to select a predetermined contact position forselecting a desired one of said selector switches,

a power operator for said master starter switch and said mastersupplemental switch,

means for energizing said master starter switch power operator throughthe corresponding one of said second contact means and the predeterminedcontact position of said master switch bank upon the desired selectorswitch being actuated to open said first contact means and close saidsecond contact means thereof,

means including said gang switch means to establish a shunt circuitaround the actuated open first contact means of the actuated selectorswitch upon the desired selector switch being actuated,

and means for energizing said controllable device through the remainingones of said first contact means and through said shunt circuit upon thedesired selector switch being actuated.

3. A control circuit comprising, in combination, first and second leads,

means to connect said leads to a power supply,

a controllable device,

a master starter switch,

a plural number of selector switches each having first and secondcontact means with one thereof being open and the other thereof beingclosed,

said plurality of selector switches arranged to be actuable to open saidfirst contact means and to close said second contact means,

means connecting said first contact means of said selector switches andsaid master starter switch in series through said controllable devicebetween said first and second leads,

a master switch bank having contacts arranged to correspond to each ofsaid selector switches,

a movable device in said switch bank engageable with the contactstherein to select a predetermined contact position for selecting adesired one of said selector switches,

a power operator for said master starter switch,

means for establishing a circuit from said first to said second leadthrough the corresponding one of said second contact means and thepredetermined contact position of said master switch bank and saidmaster starter switch power operator upon the desired selector switchbeing actuated to open said first contact means and close said secondcontact means thereof,

and means including said master switch bank establishing a shunt circuitaround the actuated open first contact means of the actuated selectorswitch to establish a connection between said first and second leadsthrough said master starter switch and said controllable device upon thedesired selector switch being actuated.

4. A control circuit comprising, in combination, first and second leads,

means to connect said leads to a power supply,

a controllable device,

a master starter switch and master supplemental switch,

a plural number of selector switches each having first and secondcontact means with one thereof being open and the other thereof beingclosed,

said plurality of selector switches arranged to be actuable to open saidfirst contact means and to close said second contact means,

means connecting said first contact means of said selector switches andsaid master starter switch in series through said controllable devicebetween said first and second leads,

gang switch means having a master switch bank and a shunt circuit bank,

contacts in each switch bank arranged to correspond to each of saidselector switches,

a movable device in each of said banks for sequentially engaging thecontacts therein to select a predetermined contact position forselecting a desired one of said selector switches,

a power operator for said master starter switch and said mastersupplemental switch,

means for establishing a circuit from said first to said second leadthrough the corresponding one of said second contact means and thepredetermined contact position of said master switch bank and saidmaster starter switch power operator upon the desired selector switchbeing actuated to open said first contact means and close said secondcontact means thereof,

and means including said gang switch means establishing a shunt circuitaround the actuated open first contact means of the actuated selectorswitch to establish a connection between said first and second leadsthrough said master starter switch and said controllable device uponthe-desired selector switch being actuated.

5. A control circuit comprising, in combination, first I and secondleads,

It) able to open and first contact means and to close said secondcontact means,

means connecting said first contact means of said selector switches andsaid master starter switch in series through said controllable devicebetween said first and second leads,

a master switch bank having contacts arranged to correspond to each ofsaid selector switches,

a movable device in said switch bank engageable with the contactstherein to select a predetermined contact position for selecting adesired one of said selector switches,

a power operator for said master starter switch,

a shunt circuit for each of said first contact means of said selectorswitches,

each said shunt circuit including the series combination of therespective second contact means and the predetermined contact positionof said switch bank,

means for establishing a circuit from said first to said second leadthrough the corresponding one of said second contact means and thepredetermined contact position of said master switch bank and saidmaster starter switch power operator upon the desired selector switchbeing actuated to open said first contact means and close said secondcontact means thereof,

and said shunt circuit for the actuated selector switch establishing aconnection between said first and second leads through said masterstarter switch and said controllable device upon the desired selectorswitch being actuated.

6. A control circuit comprising, in combination, first and second leads,

means to connect said leads to a power supply,

a controllable device,

a master starter switch and a master suplemental switch,

a plural number of selector switches each having first and secondcontact means with one thereof being open and the other thereof beingclosed,

said plurality of selector switches arranged to be actuable to open saidfirst contact means and to close said second contact means,

means connecting said first contact means to said selector switches andsaid master starter switch in series through said controllable devicebetween said first and second leads,

gang switch means having a master switch bank and a shunt circuit bank.

contacts in each switch bank arranged to correspond to each of saidselector switches,

a movable device in each of said banks engageable with the contactstherein to select a predetermined contact position for selecting adesired one of said selector switches,

a power operator for said master starter switch and said mastersupplemental switch,

a shunt circuit for each of said first contact means of said selectorswitches,

each said shunt circuit including the series combination of therespective second contact means, the predetermined contact position ofsaid two switch banks and said master supplemental switch,

means for establishing a circuit from said first to said second leadthrough the corresponding one of said second contact means and thepredetermined contact position of said master switch bank and saidmaster starter switch power operator upon the desired selector switchbeing actuated to open said first contact means and close said secondcontact means thereof,

and said shunt circuit for the actuated selector switch establishing aconnection between said first and second leads through said masterstarter switch and said controllable device upon the desired selectorswitch being actuated.

7. In a tool pool having a plural number of unlike receptacles formed toaccept only the complementary switch operating extension on acorresponding tool,

the provision of, first and second leads,

means to connect said leads to a power supply,

a controllable device including a push button switch and a poweroperated machine starting device,

a master starter switch and a master supplemental switch,

a plurality of extension operated switches equal in number to saidplural number and each having a normally open and a normally closedcontact means,

said extension operated switches arranged to be actuated by'said switchoperating extensions when said tools are placed in the pool in therespective receptacles.

means connecting said normally open contact means of said extensionoperated switches and said master starter switch in series through saidcontrollable device between said first and second leads,

gang switch means having a master switch bank and a shunt circuit bank,

contacts in each switch bank arranged to correspond to each of saidtools,

each of said banks having said plural number of contact positions,

a movable device in each of said banks engageable with the contactstherein to select a predetermined contact position for selecting adesired tool,

a power operator for said master starter switch and said mastersupplemental switch,

a shunt circuit for each of said normally open contact means in saidextension operated switches,

each said shunt circuit including the series combination of therespective normally closed contact means, the predetermined contactposition of said two banks of said gang switch means and said mastersupplemental switch,

means for establishing a circuit from said first to said second leadthrough the corresponding one of said normally closed contact means andthe predetermined contact position of said master switch bank and saidmaster starter switch power operator upon the desired tool being removedfrom the tool pool,

and said shunt circuit for the actuated extension operated switchestablishing a connection from said first lead through said masterstarter switch to said controllable device upon the desired tool beingremoved from the tool pool.

8. A control circuit comprising, in combination, first and second leads,

means to connect said leads to a power supply,

a controllable device,

a master starter switch and a master supplemental switch,

a plural number of selector switches each having first and secondcontact means with one thereof being open and the other thereof beingclosed,

said plurality of selector switches arranged to be actuable to open saidfirst contact means and to close said second contact means,

means connecting said first contact means of said selector switches andsaid master starter switch in series through said controllable devicebetween said first and second leads,

a stepping switch having a master switch bank and a shunt circuit bank,

contacts in each switch bank arranged to correspond to each of saidselector switches,

each of said banks of the stepping switch having said plural number ofcontact positions,

a movable device in each of said banks for sequentially engaging thecontacts therein,

stepping means for steppingly moving said movable device for forming asequential connection with said contacts to position said movabledevices at a predetermined contact position for selecting a desired oneof said selector switches, a power operator for said master starterswitch and said master supplemental switch, a shunt circuit for each ofsaid first contact means of said selector switches, each said shuntcircuit including the series combination of the respective secondcontact means, the predetermined contact position of said two banks ofsaid stepping switch and said master supplemental switch, means forestablishing a circuit from said first to said second lead through thecorresponding one of said second contact means and the predeterminedcontact position of said master switch bank and said master starterswitch power operated upon the desired selector switch being actuated toopen said first contact means and close said second contact meansthereof, and said shunt circuit for the actuated selector switchestablishing a connection between said first and second leads throughsaid master starter switch and said controllable device upon the desiredselector switch being actuated. 9. In a tool pool having a plural numberof unlike receptacles formed to accept only the complementary switchoperating extension on a corresponding tool,

the provision of, first and seconds leads,

means to connect said leads to a power supply,

a controllable device including a push button switch and a poweroperated machine starting device,

a master starter switch and a master supplemental switch,

a plurality of extension operated switches equal in number to saidplural number and each having a normally open and a normally closedcontact means,

said extension operated switches arranged to be actuated by said switchoperating extensions when said tools are placed in the pool in therespective receptacles,

means connecting said normally open contact means of said extensionoperated switches and said master starter switch in series through saidcontrollable device between said first and second leads,

a stepping switch having a master switch bank and a shunt circuit bank,

contacts in each switch bank arranged to correspond to each of saidtools,

each of said banks of the stepping switch having said plural number ofcontact positions,

a movable device in each of said banks for sequentially engaging thecontacts therein,

- stepping means for steppingly moving said movable device for forming asequential connection with said contacts to position said movabledevices at a predetermined contact position for selecting a desired tooa power operator for said master starter switch and said mastersupplemental switch,

a shunt circuit for each of said normally open contact means in saidextension operated switches,

each said shunt circuit including the series combination of therespective normally closed contact means, the predetermined contactposition of said two banks of said stepping switch and said mastersupplemental switch,

means for establishing a circuit from said first to said second leadthrough the corresponding one of said normally closed contact means andthe predetermined contact position of said master switch bank and saidmaster starter switch power operator upon the desired tool being removedfrom the tool pool,

and said shunt circuit for the actuated extension operated switchestablishing a connection from said first lead through said masterstarter switch to said controllable device upon the desired tool beingremoved from the tool pool.

3,273,023 13 10. In a tool pool having a plural number of unlikereceptacles formed to accept only the complementary switch operatingextension on a corresponding tool, the provision of,

14 a power supply with a power supply conductor and a return conductor,a master starter switch and a master supplemental switch,

a power supply with a power supply conductor and a a plurality ofextension operated switches each havreturn conductor, ing a normallyopen and a normally closed contact a master starter switch and a mastersupplemental means,

switch, said extension operated switches arranged to be actua pluralityof extension operated switches each having ated by said switch operatingextensions when said a normally open and a normally closed contact toolsare placed in the pool in the respective receprneans, tacles, saidnormally open contact means of said said extension operated switchesarranged to be actuextension operated switches providing a closedconated by said switch operating extensions when said nection from thepower supply conductor to said tools are placed in the pool in therespective recepmaster starter switch when all said tools are in placetacles, said normally open contact means of said ex- 15 in the toolpool, tension operated switches providing a closed conneca steppingswitch having a master switch bank and a tion from the power supplyconductor to said master supplemental circuit bank, starter switch whenall said tools are in place in the contacts in each switch bank arrangedto correspond tool pool, to each of said tools, a stepping switch havinga master switch bank and a each of said banks of the stepping switchhaving said supplemental circuit bank, plural number of contactpositions, contacts in each switch bank arranged to correspond o amovable device in each of said banks for sequentially each of saidtools, engaging the contacts therein, each of said banks of the steppingswitch having said Stepping means for steppingly moving said movabledeplural number of contact positions, vices for forming a sequentialconnection with said a movable device in each of said banks forsequentially contacts to position said movable devices at a preengagingthe contacts therein, determined position for selecting a desired tool,stepping means for steppingly moving said movable dea power operatedmaster switch operator,

vices for forming a sequential connection with said means for connectingthe power supply conductor contacts to position said movable devices ata prethrough the corresponding one of said normally determined positionfor selecting a desired tool, closed contact means with said masterswitch operaa power operated master switch operator, tor upon thedesired tool being removed from the means for connecting the powersupply conductor tool pool,

through the corresponding one of aid normally means comprising aselected contact in said suppleclosed contact means with said masterswitch operamental circuit switch bank for connecting said master torupon the desired tool being remov d fro the supplemental switch withsaid master starter switch tool pool, upon the stepping switch movabledevices being means comprising a selected contact in said supplemoved toai p edetermined position,

mental circuit switch bank for connecting said master a Power e h ing ap wer operated machine starting supplemental switch with said masterstarter switch device Connected therein, upon h Stepping i h bl devicesbeing and means for connecting said starting device with said moved tosaid predetermined position, master Starter Switcha 521 5; gi i zgig fglOperated machme startmg References Cited by the Examiner and means forconnecting said starting device with said master starter switch.

11. In a tool pool having a plural number of unlike UNITED STATESPATENTS receptacles formed to accept only the complementary switchoperating extension on a corresponding tool, the provision of,

NEIL C. READ, Primary Examiner. D. YUSKO, Assistant Examiner.

1. A CONTROL CIRCUIT COMPRISING, IN COMBINATION, A CONTROLLABLE DEVICE,A MASTER STARTER SWITCH, A PLURAL NUMBER OF SELECTOR SWITCHES EACHHAVING FIRST AND SECOND CONTACT MEANS WITH ONE THEREOF BEING OPEN ANDTHE OTHER THEREOF BEING CLOSED, A MASTER SWITCH BANK HAVING CONTACTSARRANGED TO CORRESPOND TO EACH OF SAID SELECTOR SWITCHES, A MOVABLEDEVICE IN SAID SWITCH BANK ENGAGEABLE WITH THE CONTACTS THEREIN TOSELECTED A PREDETERMINED CONTACT POSITION FOR SELECTING A DESIRED ON OFSAID SELECTOR SWITCHES, A POWER OPERATOR FOR SAID MASTER STARTER SWITCH,MEANS FOR ENERGIZING SAID MASTER STARTER SWITCH POWER OPERATOR THROUGHTHE CORRESPONDING ONE OF SAID SECONE CONTACT MEANS AND THE PREDETERMINEDCONTACT POSITION OF SAID MASTER SWITCH BANK UPON THE DESIRED SELECTORSWITCH BEING ACTUATED TO OPEN SAID FIRST CONTACT MEANS AND CLOSED SAIDSECOND CONTACT MEANS THEREOF, MEANS INCLUDING SAID MASTER SWITCH BANK TOESTABLISH A SHUNT CIRCUIT AROUND THE ACTUATED OPEN FIRST CONTACT MEANSOF THE ACTUATED SELECTOR SWITCH UPON THE DESIRED SELECTOR SWITCH BEINGACTUATED, AND MEANS FOR ENERGIZING SAID CONTROLLABLE DEVICE THROUGH THEREMAINING ONE OF SAID FIRST CONTACT MEANS AND THROUGH SAID SHUNT CIRCUITUPON THE DESIRED SELECTOR SWITCH BEING ACTUATED.